Shouldn't be it's not mentioned here http://www.motuk.com/bike/7-1.asp#Menu_Top
You'd be surprised what you can get away with and pass an MOT. I passed my last one with debaffled, unmarked pipes and a bent gear linkage where I had to use a leatherman and a hammer infront of the garage to put the bike in neutral (dropped bike and bent gear linkage day before MOT), they just put an advisory as "Gear linkage slightly loose".